1. Field of the Invention
The present invention relates to leak detection in refrigeration systems, and more particularly to effective leak detection by the addition of a dye selected from the general chemical class of naphthalimide fluorescent dyes in a refrigeration system where said refrigeration system employs, in combination with a suitable refrigerant system lubricant, a material, suitable to function as a heat transfer agent or refrigerant in a hermetic system.
2. Background Art
Refrigerants that are devoid of the chlorine atom and therefore considered environmentally friendly to the earth's ozone layer have been developed and continue to be developed to replace CFC and HCFC materials that are the circulating heat transfer media in many hermetic systems. Many chemical companies have developed products that alone or in combination are suitable to function as heat transfer agents or refrigerants in a hermetic system such as, but not limited to, hydrochlorofluorocarbons (HCFC), hydrofluorocarbons (HFC) and hydrogen, halogenated or ether derivatives of methane, hydrogen, halogenated, ether or cyclic derivatives of either ethane, propane, butane, pentane, mixtures of HCFC, HFC, hydrocarbons, carbon dioxide and ammonia. These forgoing HCFC, HFC and hydrocarbon refrigerants are considered less damaging to the environment and have ozone depletion potentials which range from zero to a fraction of one, while the ozone depletion potential of a CFC refrigerant, such as CFC-12, is one.
The use of these new alternative refrigerants has required the use of new kinds of refrigeration system lubricants such as synthetic polyalkylene glycols (PAG) and polyolesters (POE) and has rendered prior leak detection chemicals employing materials such as those described in U.S. Pat. Nos. 4,758,366 and 5,149,453, issued on Jul. 19, 1988 and Sep. 26, 1992, respectively, as largely ineffective. These patents teach the use of perylene yellow fluorescent dyes formulated with mineral oils. Mineral oil is a hydrocarbon. Hydrocarbons such as synthetic hydrocarbons (SHC), alkylbenzene (AB), and polyalphaolefins (PAO) may only be partially soluble in polyalkylene glycol and in polyolester lubricants such as those used in the new HFC refrigerant-containing systems. The materials found in the above-referenced patents have been found unsuitable in actual systems tests and laboratory analytical tests for long term use in hermetic systems such as refrigeration, heating, ventilating and air conditioning systems employing the alternative HFC refrigerants. The reason for the unsuitability of these perylene dyes in HFC systems is primarily due to thermal chemical instability.
Some new HFC systems reach higher operating temperatures and pressures than the old CFC systems because of different thermodynamic properties. Such higher temperatures and pressures can adversely affect the thermal stability of the perylene dyes in the new HFC-containing systems. For these reasons, a new fluorescent dye composition for use in HFC systems that utilize refrigeration system lubricants such as mineral hydrocarbons, synthetic hydrocarbons, polyalkylene glycols and polyolesters is required.